Forced air systems for commercial and residential buildings are typified by having a series of ducts which run from the source of hot air such as the furnace to the various spaces to be heated, each duct containing a separate damper control or vane to regulate the relative amount of air passed through each duct. In solar heating units which employ forced air as the heat supply medium, additional considerations are involved in that air or other fluid must be distributed across a solar collector which is located externally of the building and returned either to a heat storage area or directly to a space to be heated, depending upon whether there is any immediate demand for the supply of hot air to the space. During periods when there is no heat available from the solar collector, however, the storage area must provide heat to the space when required; or if heat is not available from the space or from the solar collector an auxiliary heat source must be available to supply the necessary heat to the space.
In the past due to variable demand in heat and fluctuations in the amount of heat available either from the solar collector or the storage area, rather elaborate ducting systems have been provided by requiring separate damper controls, thermostats and blowers for maintaining the temperature at the desired level in the space to be heated. Representative of such systems are those disclosed in the patents to Groth U.S. Pat. No. 4,029,258, Pulver U.S. Pat. No. 3,994,276, Lof U.S. Pat. No. 2,680,565 and Gay U.S. Pat. No. 2,559,871. Still another patent of interest is to Mason U.S. Pat. No. 3,997,108 which attempts to consolidate the duct system so as to be capable of moving air either from the solar collector to the storage area or directly to the space; or directly from the storage area to the space all under the influence of a single blower. However, the system requires utilization of dampers in series under independent damper drives which are regulated by thermostats to determine the relative amount of air drawn from the solar collector or from the heat storage area to the space or area to be heated.